One of the application areas for magnetic field sensor elements is, for example, that of motor vehicles. Among their tasks in this area is use in air springs for determining the level of the vehicle in a level measuring device. DE 100 23 622 B4, which is incorporated by reference, describes in this respect the use of the magnetic field strength of a permanent magnet, sensed by a magnetic field sensor element, for level determination.
Similarly, magnetic field sensor elements may be used for controlling a reciprocating-piston internal combustion engine, such as that typically used in a motor vehicle. DE 10 2005 035 881 A1 and EP 1 310 634, which are incorporated by reference, show the use of magnetic field sensor elements for sensing the rotational angular position of a camshaft, from which the necessary values for adjusting the camshaft in relation to the crankshaft can be calculated.
Magnetic field sensors may also be used for sensing the surroundings of the motor vehicle as a component part of a safety device. In this case, items of image information, such as those described in DE 102 12 483 A1, which is incorporated by reference, from the surroundings of the motor vehicle, for example of stationary and/or movable objects and/or road users, are recorded and assessed, the assessment possibly leading to triggering of one or more airbags, dependent on the seating occupancy in the motor vehicle. Coupling with a parking system is also possible.
Magnetic field sensor elements are used, for example, for determining the wheel speed, that is to say the rotational speed of a wheel. These are known as wheel speed sensors.
The speed determination typically takes place by using three elements:                a sensor with a sensor head        a magnetic track (encoder)        an air gap between the two hardware elements.        
As a result of the way in which they are designed, magnetic field sensor elements have only a small range. Therefore, to function well, they should be positioned as close as possible to the recording magnetic track, known as the encoder.
Wheel speed sensors usually operate with two different types of encoder:
Ferromagnetic Encoder
The ferromagnetic encoder influences the magnetic field that is generated by the magnet of the sensor element.
Magnetic Encoder
The magnetic encoder generates its own magnetic field. It typically consists of elastomer with a so-called filler comprising a ferrite content of 20%.
The advantages of a magnetized encoder are that it can be easily integrated in other mechanical components and/or subassemblies, preferably in the seal of the wheel bearing. It can, however, also assume an additional, independent function as a seal of the wheel bearing. On account of their technology, the sensor elements for the magnetized encoder require little space, and therefore make a particularly small sensor head possible.
There are known wheel speed sensors that have their housed magnetic field sensor elements, that is to say bridges, dies, ASICs, magnets or leadframes, encapsulated in epoxy, and for positionally exact positioning have to be fitted in prefabricated plastic or plastic-metal inserts known as carriers, or in a so-called pre-molds performing the task of pre-encapsulation.
These carriers or pre-molds are held in the encapsulating mold exactly in position for the sensor unit with the magnetic field sensor and (read head), in order to ensure the positional exactness of the sensor element during the encapsulation to form the finished sensor. The necessary sealing of the sensors in the region of the carrier holding points is achieved here by the plastics material bonding for the encapsulation of the sensor unit as well as by the forming of a number of melt ribs at the holding points.